Andalusian researchers led by the University of Granada, have discovered that members of the human lineage, classed as the genus Homo are the only primates throughout their 2.5-million year history, whose size of teeth has decreased as their brain size increased.

The key to this phenomenon, which scientists call "evolutionary paradox", could be in how Homo's diet has evolved.

Digestion starts first in the mouth and, so, teeth are essential in breaking food down into smaller pieces. Therefore, the normal scenario would be that, if the brain grows in size, and, hence, the body's metabolic needs, so should teeth.

However, in the case of Homo, this has not been the case, according to the scientists.

The main author of the study, researcher Juan Manuel Jimenez Arenas, from the University of Granada's Department of Pre-History and Archaeology, points out that "This means that significant changes must have occurred in order to maintain this trend".

A change in diet, incorporating a higher amount of animal food, must have been one of the keys to this phenomenon. The quality leap in Homo's diet, through a greater intake in animal proteins, fats and certain olio-elements, is essential for a correct working and maintenance of the brain.

On a similar note, a larger brain allows greater social and cultural development, which, at that time, led to the achievement of important technological innovations.